Workflow systems typically have a process model with multiple instances which are concurrently operating according to this model. If the process needs to be modified a new process model is deployed and new instances can be created with the new model. However, existing instances created by the earlier model generally must run to completion against their creation model version. This structure means that while new instances will pick up the process modifications, prior instances usually must continue to run against the earlier process model. Long running processes, which run for weeks or even months, emphasize this challenge because of the long time periods during which the old and new models can overlap. The limitation that instances generally must run to completion against the creation model is a significant impediment to the adaptability of the workflow model. The nature of long running processes means that it is possible that during the lifetime of a running process instance changes to the process model may be required.